Conventionally, in a sealing structure including a gasket attached to a fitting groove, a structure is known in which a protrusion is provided on the gasket or the fitting groove so that the gasket is prevented from coming out of the fitting groove by utilizing elastic repulsive force generated from a portion of the gasket that is being compressed in a groove width direction (see Patent Document 1).
However, if a structure as described above is employed in a case of a gasket having a small cross sectional size, there is a possibility that such a gasket may be twisted or abnormally deformed at the time of fitting because the whole gasket tends to deform easily. Accordingly, such a gasket is difficult to fit in an appropriate position and is prone to come out easily.